PENGARUH AUSTEMPER TEMPERATUR QUENCH 450oC DAN 500oC DENGAN VARIASI HOLDING TIME 1,5 JAM, 2 JAM DAN 2,5 JAM TERHADAP KEKERASAN DAN STRUKTUR MIKRO BESI COR KELABU PADUAN 0,4% TEMBAGA (Cu)

Abstract

Gray cast iron is the biggest foundry product. Because of good mechanical property, it is used for part of machine. The advantage of property can infect scientist to improve research on this material. From this research, we can get a good mechanical property of gray cast iron. Mechanical property can be improved by alloying with other materials that have function of carbide stabilitator. Copper is carbide stabilitator that can be added for casting of gray cast iron. To identify this characteristic, brinell hardness can detect a change of property that is alloyed by copper. The change include hardenabillity of gray cast iron especially hardness. The other way, we can use heat treatment which effect mechanical property. Austempering which used by heating material to autenite temperature that have purpose to get bainit structure. By austempering process, we can increase hardenabillity and toughness of gray cast iron. This treatment occur from 3500C to 5000C with holding time variations. This research use three variation of holding time : 1,5 h, 2 h and 2,5 h. We use salt bath to quench this material. With Brinell, austemper process can increase about 218 HBN at 4500C (2 h) that has different value at 1,5 h (192 HBN) and 2,5 h (205 HBN). At 5000C, we get about 212 HBN at 2 h. The holding time at 2 h has optimum value of hardness. The other of holding time get 184 HBN (1,5 h) and 195 HBN (2,5 h). Key words : Mechanical property, brinell hardness, austemper, micrographic structure of gray cast iron.